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Message-ID: <9fa13591-38dc-5dbf-5271-5c2bd364f16f@linux.intel.com>
Date: Mon, 31 Jul 2023 16:02:09 +0200
From: Alexander Antonov <alexander.antonov@...ux.intel.com>
To: "Colin King (gmail)" <colin.i.king@...il.com>
Cc: linux-perf-users@...r.kernel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: potential return of uninitialized variable ret in function
skx_upi_topology_cb
Hi Colin,
Thank you so much for reporting the issue. Seems fix wasn't picked up
before, I will resend it.
Thank you
On 7/27/2023 3:55 PM, Colin King (gmail) wrote:
> Hi,
>
> Static analysis with cppcheck has detected a potential return of an
> uninitialized variable in function skx_upi_topology_cb. The issue was
> introduced with commit:
>
> commit 4cfce57fa42d277497cd2c425021312eae2f223c
> Author: Alexander Antonov <alexander.antonov@...ux.intel.com>
> Date: Thu Nov 17 12:28:28 2022 +0000
>
> perf/x86/intel/uncore: Enable UPI topology discovery for Skylake
> Server
>
> static int skx_upi_topology_cb(struct intel_uncore_type *type, int
> segment,
> int die, u64 cpu_bus_msr)
> {
> int idx, ret;
>
> ^^ ret is not initialized
>
> struct intel_uncore_topology *upi;
> unsigned int devfn;
> struct pci_dev *dev = NULL;
> u8 bus = cpu_bus_msr >> (3 * BUS_NUM_STRIDE);
>
> for (idx = 0; idx < type->num_boxes; idx++) {
> upi = &type->topology[die][idx];
> devfn = PCI_DEVFN(SKX_UPI_REGS_ADDR_DEVICE_LINK0 + idx,
> SKX_UPI_REGS_ADDR_FUNCTION);
> dev = pci_get_domain_bus_and_slot(segment, bus, devfn);
>
> ^^ dev may be null, so ret is never assigned
>
> if (dev) {
> ret = upi_fill_topology(dev, upi, idx);
> if (ret)
> break;
> }
> }
>
> pci_dev_put(dev);
> return ret;
> }
>
> I suspect this probably is very unlikely, but it would be useful to
> have ret initialized to some value to avoid garbage being returned.
> Not sure what the best value is to set as as default in this corner case.
>
> Colin
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